The present invention relates to capacitive touch-pads and, more particularly, to a novel laminated capacitive touch-pad providing greater dielectric coupling between touch plate and transmit and receive electrodes thus greatly enhancing the ratio of desired coupling capacitance to parasitic coupling between transmit and receive electrodes while maintaining required high voltage insulation parameters and facilitating a greater total dielectric thickness which is required in some applications.
Touch-pads capable of changing capacitance, when approached or contacted, are well known. Capacitive touch-pads are often used in high voltage environments where relatively thick dielectrics are required for safety purposes; the value of a parasitic capacity between a pair of spaced transmitting and receiving electrodes, fabricated upon a first surface of a relatively thick dielectric substrate, often approaches the capacitance value between each of the electrodes and a touch-pad electrode fabricated upon the remaining surface of the substrate, whereby erroneous signals are frequently generated. The problem is compounded when arrays of discrete touch-pad devices are utilized; the separation distance between each device in the array and all other adjacent devices must be relatively great to prevent additional parasitic capacitance, and the associated signal leakage attributable thereto, from totally masking the desired change in signal when the touch electrode is approached and/or contacted. A capacitive touch-pad having a relatively large ratio of desired coupling capacity to parasitic capacity, yet retaining a relatively thick dielectric for safety reasons in high voltage environments, is desirable.